Foodborne diseases (FBD) are the infectious and toxic diseases caused by agents that enter the body through the ingestion of food (velusamy et al., 2010). These agents commonly referred to as pathogens include bacteria, viruses, parasites, toxins and metals. These agents can also be transmitted through the food chain reaching humans. For example, Salmonella spp. is a bacterial zoonotic pathogen, and is ubiquitous in the environment. They are commonly found in the gut and intestinal tract of animals including farmed, domestic and wild animals. There are numerous routes through the food chain (Herman et al., 2008). Salmonella is one of the most common pathogen causing human bacterial gastroenteritis. This has been outlined in various reports (EFSA, 2010). It is known that in the European Union countries there has been a total of 131,468 confirmed cases of human salmonellosis in the year 2008 (Zweifel et al., 2012). Poultry and eggs are considered to be the most important carriers for these foodborne diseases especially for Salmonella and Campylobacter which can be transmitted to humans. In Saudi Arabia, food of poultry origin causes 29.3% of poisoning cases (Haider and EL-Eied, 2005). Salmonellosis is a public health concern. An estimated 93.8 million cases of gastroenteritis are developed in places such as tropical countries, Europe, United-States, South America, Asia (Rane, 2011; Borges et al., 2013; Henry et al., 2013). Generally human salmonellosis cases are associated with consumption of contaminated egg, poultry products (Zaki et al., 2009). It has been reported that about 90-95% of non-typhoid salmonellosis increases by consumption of contaminated food-stuffs (poultry and other meat products) (Andreoletti et al., 2008). Previous studies showed that salmonellae are present in poultry processing wastes in a surprisingly constant relation with fecal coliforms (in excess of 1 Salmonella per 500 fecal coliforms) (Hoadley et al., 1974). Salmonella Enteritidis and Salmonella Typhimurium are typical serovars belonging to the S. enterica subspecies (79.9% of all known serovars in human cases), significant causes of foodborne illness in humans with 95,548 reported cases in the European Union in 2011 (Zweifel and Stephan, 2012; Ahmed et al., 2014). However, it has been reported that S. Enteritidis is reported more frequently than S. Typhimurium in many European countries. Both of these bacteria are currently the most widely spread critical pathogens causing foodborne illnesses in humans and animals (Park et al., 2014).
Staphylococcus aureus is also considered one of the most common sources of food poisoning resulting from consumption of contaminated food (EI-Jakee et al., 2013), raw meat, meat product, dairy products and ready-to-eat foods. For example, it is one of the top five pathogens that contribute to the most foodborne illnesses in America. About 76 million cases of illnesses and 5000 deaths are reported each year according to the Centre for Disease Control and Prevention (2012) (World Health Organization, 2007; Sung et al., 2013). Staphylococcus aureus enterotoxins (SEs) which contains some proteins that have a thermo-stability extra-cellularly are caused by S. aureus. Staphylococcal food poisoning (SFP) caused by the ingestion of food contaminated with SEs is the second most commonly reported foodborne illness (Argudin et al., 2010). After food poisoning by Staphylococcus aureus, symptoms usually appear within a few hours of eating the contaminated food. The most common symptoms are nausea, vomiting, abdominal cramping, and prostration. Food that is most frequently infected by Staphylococcus aureus includes meat and meat products, poultry and egg products (Stehulak, 2011).
Different methods depending on various scientific principles are used for the detection of pathogenic bacteria relating foodborne diseases. Conventional methods include culture-depending methods, microscopic, PCR, serological and biochemical methods. These methods are still used but they generally present some disadvantages. For example, they are time-consuming, expensive and have and a limited sensitivity. Immunoassay is one of the detection methods which depends on the antigen-antibody reaction resulting in a production of a signal which can be measured (fingerova et al., 2011). This technique is widely used for detection of pathogens (Webster et al., 2004) and food toxins like mycotoxins (Casale et al., 1988). Many types of immunoassay techniques are available such as ELIZA, immunomagnetic, immunofluorescence and radioimmunoassay. Among these techniques microtitre plate-based and lateral flow methods are the most commonly used in agricultural biotechnology (Shan, 2011). Immunoassay methods provide some advantages over conventional methods. For example, high specificity, sensitivity and portability. Accordingly, most immunoassay tests can be achieved utilizing kits or small apparatuses (Lesnik, 2000). This facilitates onsite and point-of-care analysis. Optical immunoassay including fluorescence, chemiluminscence, electrochemiluminscence, surface Plasmon resonance which combine antigen-antibody reaction with optical measurements are one of the most common immunoassay techniques. This is because it uses visible light radiation. Also, a rapid signal production is obtained which decreases the time needed to complete the bioassay test. Use of nanoparticles such as magnetic beads and fluorescent beads can improve sensitivity and performance of optical immunosensors (Tang et al., 2013), magnetic-bead based enzyme immunoassay with fluorescence has been used for detection of Bacillus globigii spores and B. globigii (Farrell et al., 2005).
Recent trends in food technology and the increasing interest in food safety and quality have led microbiologists to explore and develop new and rapid detection methods which can give precise results in the shortest time (Dostalek et al., 2005).
There is still a need for more simple, efficient and low-cost methods for detecting microorganisms.